Why you get the error message, @mhoran_psprep explained that. Now if you still want to achieve something like that, the closest thing is to choose a keyword, that is likely to appear in every other tweet and search with that + the source. There is no word like that, so I chose a letter. :P

I searched with the letter a and the source as tweetdeck.

http://search.twitter.com/search.json?q=a%20source:tweetdeck

The search works. The character a is likely to appear in most tweets. You can choose any other letter too. See if this works for you too. :)